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Tohatsu MFS25A / MFS30A (carbureted) service guide

Oil, gear oil, spark plugs and the service schedule for the Tohatsu MFS25A / MFS30A (carbureted) (25 to 30 hp, four-stroke), from the factory service manual, plus how we service it in Hawaiʻi.

Models covered: MFS25A and MFS30A, types MF, EF, EP, S / L / UL transom. 4-stroke 3-cylinder, 492 mL (30.02 cu in), 59 x 60 mm, OHC, carburetor with acceleration pump, CD ignition.

Quick answers

How much oil does a Tohatsu MFS25A / MFS30A take?
1,800 mL (1.90 US qt) with filter; 1,600 mL (1.69 US qt) without filter (upper dipstick mark).
What engine oil does a Tohatsu MFS25A / MFS30A use?
SAE 10W-30/40, API SF, SG, SH or SJ.
What gear oil does a Tohatsu MFS25A / MFS30A use, and how much?
Genuine gear oil or GL5, SAE #80 to #90. Quantity: 280 mL (9.5 US fl oz) approx.; fill from the lower plug hole until oil comes out the upper hole.
What spark plug does a Tohatsu MFS25A / MFS30A use?
NGK DCPR6E. Gap: 0.8 to 0.9 mm (0.032 to 0.035 in).
How often should a Tohatsu MFS25A / MFS30A be serviced?
The factory schedule lists: First 20 hours or 1 month; Every 50 hours or 3 months; Every 100 hours or 6 months; Every 200 hours or 12 months; Every 300 hours or 18 months; Every 400 hours or 24 months. In Hawaiʻi's salt water we do a full yearly service every 200 hours or 1 year, whichever comes first, and a new engine needs its first (break-in) service.
When should the water pump impeller be replaced on a Tohatsu MFS25A / MFS30A?
The factory schedule says to inspect it at 50 hours, 100 hours, 200 hours, 300 hours and 400 hours. In Hawaiʻi's warm salt water we replace it every 200 hours or 1 year, whichever comes first, because a worn impeller is the most common cause of overheating.
What is the idle speed of a Tohatsu MFS25A / MFS30A?
950 r/min in neutral (clutch released); trolling in forward 900 r/min.
What is the propeller nut torque on a Tohatsu MFS25A / MFS30A?
25 N·m (2.5 kg-m, 18 lb-ft), M12 x 1.5.

Maintenance specs

Engine oilSAE 10W-30/40, API SF, SG, SH or SJ
Engine oil quantity1,800 mL (1.90 US qt) with filter; 1,600 mL (1.69 US qt) without filter (upper dipstick mark)
Engine oil drain plug23.7 N·m (2.4 kg-m, 17 lb-ft), M14 x 1.5; oil the gasket
Gear oilGenuine gear oil or GL5, SAE #80 to #90
Gear oil quantity280 mL (9.5 US fl oz) approx.; fill from the lower plug hole until oil comes out the upper hole
Gear oil plugsInstall the upper plug first, then the lower.
Spark plugNGK DCPR6E
Spark plug gap0.8 to 0.9 mm (0.032 to 0.035 in)
Spark plug torque15 to 20 N·m (1.5 to 2.0 kg-m, 11 to 14 lb-ft)
Idle speed950 r/min in neutral (clutch released); trolling in forward 900 r/min
ThermostatStarts opening 60 °C ± 1.5 °C (140 ± 3 °F); fully open 75 °C (167 °F); lift 3 mm (0.12 in) or more
AnodesGear case anode (also the trim tab) and cylinder block anode on the back of a cap; replace at 2/3 of original size; no oil or paint; tighten the fixing bolt at every inspection
Propeller nut25 N·m (2.5 kg-m, 18 lb-ft), M12 x 1.5
Valve clearanceIN 0.13 to 0.17 mm (0.005 to 0.007 in); EX 0.18 to 0.22 mm (0.007 to 0.008 in); tappet lock nut 6 to 8 N·m (4.3 to 5.8 lb-ft)
Timing beltReplace if cracked, worn, lengthened or damaged (no deflection spec). Timing: "O" on drive pulley to "O" on block, then "O I" on driven pulley to the triangle on the head.

Service schedule

The factory maintenance intervals, with what is replaced and what is checked at each. Rows marked Hawaiʻi are our shop's yearly service for salt water use.

  1. First 20 hours or 1 month

    Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin

    Check: spark plugs, fuel filter

  2. Every 50 hours or 3 months

    Replace: gear case plug gaskets, propeller cotter pin

    Check: fuel filter, gear case oil, water pump impeller, anodes

  3. Every 100 hours or 6 months

    Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin

    Check: spark plugs, fuel filter, water pump impeller, anodes

  4. Every 200 hours or 12 months

    Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin, water pump impeller

    Check: spark plugs, fuel filter, anodes

  5. Every 300 hours or 18 months

    Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin, water pump impeller

    Check: spark plugs, fuel filter, anodes

  6. Every 400 hours or 24 months

    Replace: engine oil, oil filter, oil drain plug gasket, gear case oil, gear case plug gaskets, propeller cotter pin, water pump impeller

    Check: spark plugs, fuel filter, anodes

We replace the water pump impeller at every service from 200 hours up, which can be sooner than the factory schedule, because of Hawaiʻi’s warm salt water.

Source: Tohatsu service manual 25A/30A, copyright 2007. Specs can change by model year and serial number, so always confirm your exact model from the serial tag on the clamp bracket.

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